How do you make a banker happier and more productive? Pay them a bigger bonus? Wrong. The right thing to do could be to make them give to charity, and make them give big.

On Monday, FN reported that French bank BNP Paribas was offering its UK staff the option of paying a proportion of their bonus to a designated charity (the bank’s Rescue and Recover fund, which offers aid victims of humanitarian disasters) and have that donation matched by the bank from €100 to €500,000.

Other banks have similar schemes. Goldman Sachs has its Matching Gift Program, which matches employees’ donations – from $50 to $20,000 – to charities . In 2011, Credit Suisse’s US managing directors gave 2.5% of bonuses to charity. In its heyday, Bear Stearns also required executives to give to charity.

Giving to charity is obviously a great idea, and BNP Paribas & co should be rightly lauded. But they should also raise their minimum giving price, and by doing so, make bankers more productive.

A 2011 paper http://bit.ly/12WfkkC led by Michael Norton and Lalin Anik of Harvard Business School, described an experiment at an Australian bank. Within the bank, a group of employees were asked to take a voluntary survey. Some of those that undertook the survey were given charity vouchers worth $25 or $50 and asked to donate to a charity of their choice. Those who donated $50 said they were more satisfied with their jobs than those who did not receive any vouchers to distribute. And happy workers are generally more productive workers.

That giving to charity makes you feel good is not exactly ground-breaking. What was surprising was that for those at the Australian bank who donated $25, there was little difference in job satisfaction when compared with the group who had no vouchers to give.

In other words, banks that make their employees give big may end up with more productive bankers.

There is one bank that does give a lot more than anyone else to charity, and was the second-highest US corporate donor in 2011, behind Wal-Mart. This bank gave $337m, or 7% of annual profits, in 2011. Its name? Yup, you guessed it; it's that giant, blood-giving vampire philanthropist Goldman Sachs.